A small C library providing a standard interface to (non-standard) 64-bit system-alternatives of stdlib fix indexing functions.
git clone git://
Log | Files | Refs | Atom | README

commit ff7b3b19155ee0fbf0d8e7894d62074cb9e9b77b
parent 71407bba8abaaeb33f4e30061b6aeb73c9718eca
Author: gearsix <>
Date:   Fri,  7 Oct 2022 17:47:40 +0100

added:, idx_posix.c, idx_win.c, idx_win.c;

Added idxseek and idxtell support for POSIX, Windows & Unknown systems.
- POSIX calls `fseeko` and `ftello`.
- Windows calls `fseeki64` and `ftelli64`.
- For unknown systems, we just use the standard library.

Diffstat: | 43+++++++++++++++++++++++++++++++++++++++++++
Aidx_posix.c | 16++++++++++++++++
Aidx_ukwn.c | 15+++++++++++++++
Aidx_win.c | 16++++++++++++++++
4 files changed, 90 insertions(+), 0 deletions(-)

diff --git a/ b/ @@ -0,0 +1,42 @@ + +# idx.h + +**idx.h** is a small C library that provides a standard interface to the (non-standard) 64-bit system-alternatives of the standard library file indexing functions: `fseek` and `ftell`. These alternatives are required if you want to index a file that's potentially larger than 2GB (32-bits). + + +## Background + +This library exists because the standard library functions `fseek` and `ftell` are limited to using `long int` values (not even an `unsigned long int`). A `long int` has been defined as "at least 32-bits wide" in standard C; this limits the `fseek` and `ftell` to indexing files that are 2GB at most, which for some cases makes them fairly useless. +The reason these functions use this data type is because they are from the pre-standard C days, before fixed-width data types and `long long int`, where `long int` was just a 'big integer' and not necessarily a 32-bit integer. + +Unfortunately, while the ISO-C committee standardised fixed-width data types with `stdint.h` in C99, they never added updated versions of functions that used the (now-defined, ergo limit) data types. This means that to index a file larger than 2GB on a modern system using C requires you to use platform-specific alternatives, such as `fseeko` in POSIX, or `fseeki64` in Windows, etc. *Even better*, most of these alternatives were written before ISO-C introduced fixed-width data types, so they don't even make use of those nice standard data types. + +It would be nice to have a `uintmax_t ftell(FILE *stream)` on all platforms (and the same for `fseek`) but instead we have `__int64 ftelli64(FILE *stream)` on *Windows*, `off_t ftello(FILE *stream)` on *POSIX.1*, etc. + +This isn't a huge inconvenience but writing cross-platform C with a bunch of `#ifdef`s is *ugly*. **idx.h** aims to replace that inconvenience with a functions that are just as nice to use as the standard library. + + +## API + +**idx_t** - The system's own 64-bit data type. + +- `off_t` on *POSIX* +- `__int64` on *Windows* + + +**idxseek**, `idx_t idxseek(FILE *f, idx_t origin, int origin);` + +**idxtell**, `idx_t idxtell(FILE *f);` + + +## Support + +Currently support platforms are: + +- Unixes (Linux, BSD's, etc) and MacOS +- Windows + + +## Authors + +- gearsix, 2022 +\ No newline at end of file diff --git a/idx_posix.c b/idx_posix.c @@ -0,0 +1,16 @@ +#ifdef IDX_POSIX + +#include <stdio.h> + + +int idxseek(FILE *stream, idx_t offset, int origin) +{ + return _fseeko(stream, (off_t)offset, origin); +} + +idx_t idxtell(FILE *stream) +{ + return (idx_t)ftello(stream); +} + +#endif diff --git a/idx_ukwn.c b/idx_ukwn.c @@ -0,0 +1,15 @@ +#ifdef IDX_UNKW + + +int idxseek(FILE *stream, idx_t offset, int origin) +{ + return fseek(stream, (long int)offset, origin); +} + +idx_t idxtell(FILE *stream) +{ + return (idx_t)ftell(stream); +} + + +#endif diff --git a/idx_win.c b/idx_win.c @@ -0,0 +1,16 @@ +#ifdef IDX_WIN + +#include <stdio.h> + + +int idxseek(FILE *stream, idx_t offset, int origin) +{ + return _fseeki64(stream, (__int64)offset, origin); +} + +idx_t idxtell(FILE *stream) +{ + return (idx_t)_ftelli64(stream); +} + +#endif